1. Field of the Invention
The present invention relates to a DC motor brake system, and more particularly of the type that uses a solid state switching to short the motor.
2. Description of the Related Art
Many designs for DC motor brakes have been designed in the past. Current art discusses a switch being used to place a xe2x80x9cshort circuitxe2x80x9d across a turning/rotating DC motor. The kinetic needs to be dissipated for the rotating motor to stop. A rotating DC motor acts as a DC generator and the short circuit is applied to xe2x80x9cbrakexe2x80x9d the xe2x80x9cmotor/generatorxe2x80x9d. Driving a generator into a xe2x80x9cshort circuitxe2x80x9d develops an infinite current (I=E/0=dividing xe2x80x9csome voltagexe2x80x9d by zero). In this case where we are applying a short circuit, current equals voltage divided by almost zero resistance of the active switching element and internal impedance of the motor generator. This, abruptly stops the motor/generator since xe2x80x9cinfinite current requires infinite torquexe2x80x9d, and is therefore unattainable. In the present invention a very low resistance is applied to brake the motor/generator and current is thus correspondingly high.
The brakes used for D.C. motors in the past typically include a mechanical switch element. Several problems can arise since the mechanical switch cannot xe2x80x9cswitch in zero timexe2x80x9d. The mechanical switch also exhibits some mechanical xe2x80x9ccontact bouncexe2x80x9d and thus the generator does not see a resistance of xe2x80x9czero ohmsxe2x80x9d continuously. Braking action is adversely affected by some inconsistencies in switching time, contact arcing/welding of switch contacts by the high currents generated and the switch contacts and associated circuit resistances are not zero ohms. Therefore, the current is limited.
It is one of the main objects of the present invention to provide an electronic brake system for D.C. motors that eliminates the problems found with those that use mechanical components, including switch contact bouncing.
It is another object of this invention to provide an electronic brake system that allows a D.C. motor to coast to a stop irrespective of whether the power is lost.
It is still another object of the present invention to provide a very fast switching electronic brake.
It is yet another object of this invention to provide such a device that is inexpensive to manufacture and maintain while retaining its effectiveness.
Further objects of the invention will be brought out in the following part of the specification, wherein detailed description is for the purpose of fully disclosing the invention without placing limitations thereon.